This invention relates in general to an improved method and apparatus for recycling spent filter aid material for reuse.
Filter aids, such as diatomaceous earth used for precoat filtration by absorption and particle retention; pulverized activated carbon used for absorption of traces or organic matter, odor and taste; anionic and cationic resins used for ion exchange, can all be regenerated so that they can be used more than once. Heat can be used to dry the spent filter aids so completely that dissolved solids are removed from the filter aids' porous structure, so that these filter aids can be reused for further filtration. Higher temperatures can be employed for evaporation, extending regeneration for more effective and economical usage of these materials.
In K. S. Arvanitakis, U.S. Pat. No. 3,705,648, "FILTRATION SYSTEM", there is disclosed a system for filtering materials from a contaminated liquid wherein the materials removed from the liquid are expelled from the system completely dry. During the cycle of operation of the system disclosed in this patent the spent filter aid materials are removed into the contaminated liquid and in combination with new filter aid material circulated through the secondary filter to form a new filter cake precoat on the secondary filters.
Even though diatomaceous earth precoat pressure-filtration is known to have capabilities of filtering and removing sub-micron particles size solids from liquid, this process is somewhat more expensive than other filtration systems which do not use such filter aids. Due to this higher operating cost, many attempts have been made to adopt methods other than filtration, such as settling, or centrifuging which are not as effective as diatomaceous earth filtration. Completely dry discharge of the solids material from a diatomaceous earth filtration system not only provides an efficient and economical manner in which the solids material may be disposed, but affords an opportunity to recycle or reclaim the solids material in order to use them for additional filtration cycles.